For a long time there has been the need in the art for a direct current power supply which provides a load matching capability for driving a variety of electrical loads. Present day devices for supplying power to direct current loads employ voltage regulators. Conventional voltage regulation means are expensive and generally include undesirable power losses.
The present invention relates to the provisions of a direct current power supply made up of fuel cell modules and constructed to perform a voltage regulation function. Such a construction, for example, might be used to supply power to electrolytic cells or for battery charging.
To this end, the fuel cell system of the invention comprises at least one fuel cell module including a plurality of sub-stacks of fuel cells held together in a stacked arrangement, with each of the sub-stacks including a plurality of fuel cells connected in series and having cathode and anode terminals at the ends thereof. Means are provided for connecting together the anode and cathode terminals, respectively, in a parallel connection. By this arrangement the fuel cell system produces at power output terminals a voltage output the same as the voltage of each of the sub-stacks.
More particularly, the invention involves an arrangement wherein the cathode and anode terminals are provided by the module cooling means in the form of cold plates positioned between each of the sub-stacks. There are provided negative and positive coolant manifold means connected to the cold plates for providing the parallel electrical connection, with current take-off means being connected to the manifold means.
In a typical arrangement for providing a voltage regulation function, a plurality of said modules are electrically connected in series and switching means are provided for connecting a preselected number of said modules to the power output terminals of the fuel cell system. In another arrangement, sub-stacks as described above may be electrically connected in series and switching means provided for connecting a pre-selected number of said sub-stacks to the power output terminals of the fuel cell module. In accordance with another aspect of the invention, a fuel cell system is used in combination with an electrolytic cell system having operating voltage and current demand characteristics matched by the operating voltage and current output characteristics of the fuel cell system. This combination includes means for connecting the power output terminals of the fuel cell system to the power input terminals of the electrolytic cell system. In this arrangement, the fuel cell system drives the electrolytic cell system at desired operating voltage and current conditions.
It will be apparent that in the above-described combination the switching means functions to provide stepwise voltage control for use in matching the incremental voltage requirements of the electrolytic cells. Moreover, this arrangement comprises a "natural" match, i.e. one that does not require any voltage conditioning or regulating means.